Position of the third Na+ site in the aspartate transporter GltPh and the human glutamate transporter, EAAT1

Glutamate transport via the human excitatory amino acid transporters is coupled to the co-transport of three Na(+) ions, one H(+) and the counter-transport of one K(+) ion. Transport by an archaeal homologue of the human glutamate transporters, Glt(Ph), whose three dimensional structure is known is also coupled to three Na(+) ions but only two Na(+) ion binding sites have been observed in the crystal structure of Glt(Ph). In order to fully utilize the Glt(Ph) structure in functional studies of the human glutamate transporters, it is essential to understand the transport mechanism of Glt(Ph) and accurately determine the number and location of Na(+) ions coupled to transport. Several sites have been proposed for the binding of a third Na(+) ion from electrostatic calculations and molecular dynamics simulations. In this study, we have performed detailed free energy simulations for Glt(Ph) and reveal a new site for the third Na(+) ion involving the side chains of Threonine 92, Serine 93, Asparagine 310, Aspartate 312, and the backbone of Tyrosine 89. We have also studied the transport properties of alanine mutants of the coordinating residues Threonine 92 and Serine 93 in Glt(Ph), and the corresponding residues in a human glutamate transporter, EAAT1. The mutant transporters have reduced affinity for Na(+) compared to their wild type counterparts. These results confirm that Threonine 92 and Serine 93 are involved in the coordination of the third Na(+) ion in Glt(Ph) and EAAT1.     

Routine delivery of artemisinin-based combination treatment at fixed health facilities reduces malaria prevalence in Tanzania: an observational study

ABSTRACT: BACKGROUND: Artemisinin-based combination therapy (ACT) has been promoted as a means to reduce malaria transmission due to their ability to kill both asexual blood stages of malaria parasites, which sustain infections over long periods and the immature derived sexual stages responsible for infecting mosquitoes and onward transmission. Early studies reported a temporal association between ACT introduction and reduced malaria transmission in a number of ecological settings. However, these reports have come from areas with low to moderate malaria transmission, been confounded by the presence of other interventions or environmental changes that may have reduced malaria transmission, and have not included a comparison group without ACT. This report presents results from the first large-scale observational study to assess the impact of case management with ACT on population-level measures of malaria endemicity in an area with intense transmission where the benefits of effective infection clearance might be compromised by frequent and repeated re-infection. METHODS: A pre-post observational study with a non-randomized comparison group was conducted at two sites in Tanzania. Both sites used sulphadoxine-pyrimethamine (SP) monotherapy as a first-line anti-malarial from mid-2001 through 2002. In 2003, the ACT, artesunate (AS) coadministered with SP (AS + SP), was introduced in all fixed health facilities in the intervention site, including both public and registered non-governmental facilities. Population-level prevalence of Plasmodium falciparum asexual parasitaemia and gametocytaemia were assessed using light microscopy from samples collected during representative household surveys in 2001, 2002, 2004, 2005 and 2006. FINDINGS: Among 37,309 observations included in the analysis, annual asexual parasitaemia prevalence in persons of all ages ranged from 11% to 28% and gametocytaemia prevalence ranged from <1% to 2% between the two sites and across the five survey years. Amultivariable logistic regression model was fitted to adjust for age, socioeconomic status, bed net use and rainfall. In the presence of consistently high coverage and efficacy of SP monotherapy and AS + SP in the comparison and intervention areas, the introduction of ACT in the intervention site was associated with a modest reduction in the adjusted asexual parasitaemia prevalence of 5 percentage-points or 23% (p < 0.0001) relative to the comparison site. Gametocytaemia prevalence did not differ significantly (p = 0.30). Interpretation The introduction of ACT at fixed health facilities only modestly reduced asexual parasitaemia prevalence. ACT is effective for treatment of uncomplicated malaria and should have substantial public health impact on morbidity and mortality, but is unlikely to reduce malaria transmission substantially in much of sub-Saharan Africa where individuals are rapidly reinfected.     

Atomic insight into prion disorder: An intricate detail gained by 0.5 μs molecular dynamics simulation of preventive G127V and deleterious D178V mutation in prion protein

In this study we are looking into two contradicting mutations found in prion protein (PrP) viz G127V and D178V, that are reportedly protective and pathogenic, respectively. Despite significant advances in comprehension of the role of pathogenic mutations, the role of protective mutation in amyloid fold inhibition still lacks a substantial basis. To understand the structural basis of protective mutation, molecular dynamics simulation coupled with protein-protein docking and molecular mechanics/Poisson-Boltzmann surface area analysis was used to understand the instant structural variability brought about by these mutations alone and in combination on PrP and prion-prion complex. Atomic-scale investigations successfully revealed that the binding pattern of prion-prion varies differentially in protective and pathogenic mutations with secondary structure showing distinct contrasting patterns, which could supposedly be a critical factor for differential prion behavior in protective and pathogenic mutations. Considering the reported role of an amyloid fold in prion-prion binding, the contrasting pattern has given us a lead in comprehending the role of these mutations and has been used in this study to look for small molecules that can inhibit amyloid fold for prion-prion interaction in pathogenic mutant carrying PrP.     

Identification of the lipooligosaccharide biosynthetic gene cluster from Mycobacterium marinum

Lipooligosaccharides (LOSs) are antigenic glycolipids that are present in some species of Mycobacterium including the Canetti strain of M. tuberculosis. The core LOS structures from several mycobacterial organisms have been established, but the biosynthetic pathways of LOSs remain unknown. In this study, we describe two transposon insertion mutants of M. marinum that exhibit altered colony morphology. Cell wall analysis reveals that the MRS1271 mutant is defective in the synthesis of LOS-II, whereas the MRS1178 mutant accumulates an intermediate between LOS-I and -II. The genetic lesions were localized to two genes, MM2309 and MM2332. MM2309 encodes a UDP-glucose dehydrogenase that is involved in the synthesis of d-xylose. MM2332 is predicted to encode a decarboxylase. These two genes and a previously identified losA gene are localized in a gene cluster likely to be involved in the biosynthesis of LOSs. Our results also show that LOSs play an important role in sliding motility, biofilm formation, and infection of host macrophages. Taken together, our studies have identified, for the first time, a LOS biosynthetic locus. This is an important step in assessing the differential distribution of LOSs among Mycobacterium species and understanding the role of LOSs in mycobacterial virulence.     

Lamprey <Emphasis Type="Italic">snail</Emphasis> highlights conserved and novel patterning roles in vertebrate embryos

snail genes mark presumptive mesoderm across bilaterian animals. In gnathostome vertebrates, snail genes are a multimember family that are also markers of premigratory neural crest (pnc) and some postmigratory neural crest derivatives in the pharyngeal arches. Previous studies of nonvertebrate chordates indicate that they have single snail genes that retain ancestral functions in mesoderm development and perhaps in specification of a pnc-like cell population. Lampreys are the most basal extant vertebrates, with well-defined developmental morphology. Here, we identify a single snail gene from the lamprey Petromyzon marinus that is the phylogenetic outgroup of all gnathostome snail genes. This single lamprey snail gene retains ancestral snail patterning domains present in nonvertebrate chordates. Lamprey snail is also expressed in tissues that are broadly equivalent to the combined sites of expression of all three gnathostome snail paralogy groups, excepting in embryonic tissues that are unique to gnathostomes. Importantly, while snail does not appear to demarcate an early neural crest population in lampreys as it does in gnathostomes, it may be involved in later neural crest development. Together, our results indicate that significant cis-regulatory innovation occurred in a single snail gene before the vertebrate radiation, and significant subfunctionalization occurred after snail gene duplications in the gnathostome lineages.     

Implications of the genetic epidemiology of globin haplotypes linked to the sickle cell gene in southern Iran

To determine the origin of sickle cell mutation in different ethnic groups living in southern Iran, we studied the haplotype background of the betaS and betaA genes in subjects from the provinces of Fars, Khuzestan, Bushehr, Hormozgan, and Kerman and from the islands of Khark and Qeshm. beta-globin gene cluster haplotypes were determined using the PCR-RFLP technique. Detection of -alpha 3.7 deletion and beta-thalassemia mutations were defined by PCR and reverse dot blot techniques, respectively. The framework of the beta-globin gene was determined using denaturing gradient gel electrophoresis. We found that the betaS mutation in southern Iran is associated with multiple mutational events. Most of the patients were from two ethnic groups: Farsi speakers (presumably Persian in origin) from Fars province and patients of Arab origin from Khuzestan province. In both ethnic groups the Arab-Indian haplotype was the most prevalent. The frequencies of the Arab-Indian and African haplotypes in sickle cell anemia patients from the provinces of Fars and Khuzestan were similar. Among betaA chromosomes the Bantu A2 haplotype was the most prevalent. The decrease in alpha-globin production in SS patients and AS individuals appeared to be related to the reduction in mean cell volume and mean cell hemoglobin. The Arab-Indian haplotype gene flow into this region of Iran can be traced to the Sassanian Empire. It is likely that the influx of betaS genes linked to the Benin and Bantu haplotypes, of African origin, must have occurred during the Arab slave trade.     

Pyrite Suspended in Artificial Sea Water Catalyzes Hydrolysis of Adsorbed ATP: Enhancing Effect of Acetate

Minerals have been implicated in different catalytic processes during chemical evolution. It has been proposed that exergonic synthesis of pyrite (FeS₂) could have served to promote the endergonic synthesis of biomonomers in early stages of life formation on Earth. The present study was aimed to investigate whether pyrite can adsorb nucleotides and oxo acids in the potentially mild prebiotic conditions found away from the hot hydrothermal vents. It is shown that pyrite strongly adsorbs adenosine 5-triphosphate in an artificial medium that simulates primordial aqueous environments, and that adsorption is enhanced in the presence of acetate and in an oxygen-free atmosphere. Moreover, the mineral catalyzes the sequential hydrolysis of the and phosphoanhydride bonds of the nucleotide.     

IL-2-activated CD8+CD44high cells express both adaptive and innate immune system receptors and demonstrate specificity for syngeneic tumor cells

CD8(+) T cells depend on the alphabeta TCR for Ag recognition and function. However, Ag-activated CD8(+) T cells can also express receptors of the innate immune system. In this study, we examined the expression of NK receptors on a population of CD8(+) T cells expressing high levels of CD44 (CD8(+)CD44(high) cells) from normal mice. These cells are distinct from conventional memory CD8(+) T cells and they proliferate and become activated in response to IL 2 via a CD48/CD2-dependent mechanism. Before activation, they express low or undetectable levels of NK receptors but upon activation with IL-2 they expressed significant levels of activating NK receptors including 2B4 and NKG2D. Interestingly, the IL-2-activated cells demonstrate a preference in the killing of syngeneic tumor cells. This killing of syngeneic tumor cells was greatly enhanced by the expression of the NKG2D ligand Rae-1 on the target cell. In contrast to conventional CD8(+) T cells, IL-2-activated CD8(+)CD44(high) cells express DAP12, an adaptor molecule that is normally expressed in activated NK cells. These observations indicate that activated CD8(+)CD44(high) cells express receptors of both the adaptive and innate immune system and may play a unique role in the surveillance of host cells that have been altered by infection or transformation.